It is known to provide a road-speed limit for diesel engines in order to operate the diesel engine in an ecological and practical manner with respect to engine speed and fuel quantity. In this way, excessive speeds are avoided with the purpose of complying with statutory requirements and providing economical operation.
For this purpose, it is customary to provide a road-speed transducer which generates a corresponding road-speed signal and, together with other signals, interrupts or reduces the fuel metered to the engine when a pregiven threshold of maximum speed is exceeded. As a further signal, it is customary to use a signal originating from the transmission. This signal causes problems in that it can have the effect of acting as a transmission switch in neutral position and can cancel the road-speed limitation effect.
In view of the above, it cannot be excluded that by appropriate manipulation in this region, an evaluation of the signal is only possible in a deceptive manner in that the system receives the signal that the transmission switch is in the neutral position and this disables the road-speed limitation and therefore can lead to a possible dangerous driving situation as well as to technical defects. The manipulation in the above-mentioned region can be provided by a simple short-circuit of the transmission switch on the wire harness plug.